In the periodic system of DI Mendeleev, out of 110 elements, 87 are metals. They are in groups I, II, III, in side subgroups of all groups. In addition, metals are the heaviest elements of groups IV, V, VI and VII. However, many metals are amphoteric and can sometimes behave like non-metals. A feature of the structure of metal atoms is a small number of electrons in the external energy level, not exceeding three. As a rule, metal atoms have large atomic radii. In periods, alkali metals have the greatest atomic radii. They are the most chemically active, i.e. metal atoms donate electrons easily and are good reducing agents. The best reducing agents are metals of groups I and II of the main subgroups. In compounds, metals always show a positive oxidation state, usually from +1 to +4. In compounds with non-metals, typical metals form an ionic chemical bond. In the form of a simple substance, the atoms of metals are linked together by the so-called metallic bond.

A metallic bond is a special type of bond that is unique to metals. Its essence is that electrons are constantly detached from the metal atoms, which move throughout the entire mass of a piece of metal.

Metal atoms, deprived of electrons, turn into positive ions, which again attract moving electrons to themselves. At the same time, other metal atoms donate electrons. Thus, a so-called electron gas constantly circulates inside a piece of metal, which firmly binds all the atoms of the metal together. The electrons turn out to be, as it were, socialized by all the atoms of the metal. This special type of chemical bond between metal atoms determines both the physical and chemical properties of metals.

Metals have a number of similar physical properties that distinguish them from non-metals. The more valence electrons a metal has, the stronger the crystal lattice, the stronger and harder the metal, the higher its melting and boiling points, etc.

All metals have a more or less pronounced luster, which is usually called metallic, and opacity, which is associated with the interaction of free electrons with light quanta incident on the metal. Metallic luster is characteristic of a piece of metal as a whole. In powder, metals are dark in color, with the exception of silvery-white magnesium and aluminum. Aluminum dust is used to make silver-like paint. Many metals have a greasy or glassy sheen.

The color of the metals is rather monotonous: it is either silvery white (aluminum, silver, nickel) or silvery gray (iron, lead). Only gold is yellow and copper is red. According to the technical classification, metals are conventionally divided into ferrous and non-ferrous. Iron and its alloys are ferrous. All other metals are called non-ferrous.

All metals, with the exception of mercury, are solid substances with a crystalline structure, therefore their melting points are above zero, only the melting point of mercury - З9 ° C . The most refractory metal is tungsten (3380 ° C). Metals melting at temperatures above 1000 ° C are called refractory, below - fusible.

Metals have different hardness. The hardest metal is chrome (cuts glass), and the softest are potassium, rubidium, cesium. They are easy to cut with a knife.

Metals are more or less ductile (malleable). The most malleable metal is gold. It can be used to forge foil with a thickness of 0.0001 mm - 500 times thinner than a human hair. However, Mn and Bi do not have ductility - these are brittle metals.

Plasticity is the ability to deform strongly without breaking mechanical strength. Under an action that causes the displacement of particles of a body with an ionic or atomic lattice, a rupture of directed bonds occurs, and the body is destroyed. In metals, however, bonds are formed due to the electron gas. They have no direction. Therefore, the integrity of the piece of metal is preserved when the shape is changed. The ductility of metals is used in their rolling.

By density, metals are divided into heavy and light. Those with a density greater than 5 g / cm are considered heavy. The heaviest metal is osmium (22.61 g / cm). The lightest metals are lithium, sodium, potassium (density less than one). The density of a metal is the less, the less the atomic mass of the metal element and the larger the radius of its atom. Light metals - magnesium and aluminum - are widely used in industry.

Metals are characterized by high electrical and thermal conductivity. Silver is the most electrically and thermally conductive, followed by aluminum. Metals with high electrical conductivity also have high thermal conductivity. Thermal conductivity is due to the high mobility of free electrons and the vibrational motion of atoms, due to which there is a rapid equalization of temperature in the body mass. The good electrical conductivity of metals is explained by the presence of free electrons in them, which, under the influence of even a small potential difference, acquire a directional movement from the negative to the positive pole.

Metals are magnetic. Iron, cobalt, nickel and their alloys are well magnetized. Such metals and alloys are called ferromagnetic.

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Slide captions:

The position of metals in the Periodic Table of D.I. Mendeleev. Features of the structure of atoms, properties.

The purpose of the lesson: 1. On the basis of the position of metals in the PSCE, come to an understanding of the structural features of their atoms and crystals (metal chemical bonds and crystal metal lattice). 2. To generalize and expand knowledge about the physical properties of metals and their classifications. 3. To develop the ability to analyze, draw conclusions based on the position of metals in the periodic table of chemical elements.

COPPER I'm going on small coins, I like to ring in bells, They erect a monument to me for this And they know: my name is….

IRON To plow and build - he can do everything, if the coal will help him in that ...

Metals are a group of substances with common properties.

The metals are elements of I-III groups of the main subgroups, and IV-VIII groups of secondary subgroups I group II group III group IV group V group VI group VII group VIII group Na Mg Al Ti V Cr Mn Fe

Of the 109 PSCE elements, 85 are metals: they are highlighted in blue, green, and pink (except for H and He)

The position of an element in the PS reflects the structure of its atoms. POSITION OF THE ELEMENT IN THE PERIODIC SYSTEM STRUCTURE OF ITS ATOMS Ordinal number of the element in the periodic system Nuclear charge of the atom Total number of electrons Group number Number of electrons at the external energy level. Highest valence of an element, oxidation state Period number Number of energy levels. The number of sublevels at the external energy level

Sodium atom model

The electronic structure of the sodium atom

Task 2. Make a diagram of the electronic structure of the aluminum and calcium atoms in the notebook yourself, following the example with the sodium atom.

Conclusion: 1. Metals are elements that have 1-3 electrons at the external energy level, less often 4-6. 2. Metals are chemical elements whose atoms donate electrons to the outer (and sometimes pre-outer) electronic layer, turning into positive ions. Metals are reducing agents. This is due to the small number of electrons in the outer layer, the large radius of the atoms, as a result of which these electrons are weakly confined to the nucleus.

A metallic chemical bond is characterized by: - ​​delocalization of the bond, since a relatively small number of electrons simultaneously bind many nuclei; - valence electrons move freely over the entire piece of metal, which is generally electrically neutral; - the metal bond does not have directionality and saturation.

Crystalline lattices of metals

Video information about metal crystals

The properties of metals are determined by the structure of their atoms. Metal property Property property hardness All metals, except mercury, are solids under normal conditions. The mildest are sodium, potassium. They can be cut with a knife; the hardest chrome - scratches glass. density Metals are divided into light (density 5g / cm) and heavy (density greater than 5g / cm). fusibility Metals are divided into low-melting and refractory electrical conductivity, thermal conductivity Chaotically moving electrons under the action of electric voltage acquire directional motion, resulting in an electric current. metallic luster Electrons filling the interatomic space reflect light rays, and do not transmit plasticity like glass. Mechanical action on a crystal with a metal lattice only causes displacement of atomic layers and is not accompanied by bond breaking, and therefore the metal is characterized by high ductility.

Check the assimilation of knowledge in the lesson by testing 1) Electronic formula of calcium. A) 1S 2 2S 2 2P 6 3S 1 B) 1S 2 2S 2 2 R 6 3 S 2 C) 1S 2 2S 2 2 R 6 3 S 2 3S 6 4S 1 D) 1S 2 2S 2 2 R 6 3 S 2 3 R 6 4 S 2

Test tasks 2 and 3 2) The electronic formula 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2 has an atom: a) Na b) Ca c) Cu d) Zn 3) Electrical conductivity, metallic luster, plasticity, density of metals are determined: a ) the mass of atoms b) the melting point of metals c) the structure of metal atoms d) the presence of unpaired electrons

Test items 4 and 5 4) Metals interacting with non-metals exhibit properties a) oxidizing; b) restorative; c) both oxidizing and reducing; d) do not participate in redox reactions; 5) In the periodic table, typical metals are located in: a) the upper part; b) the bottom part; in the upper right corner; d) lower left corner;

Correct answers Task number Variant of correct answer 1 D 2 B 3 C 4 B 5 D

Preview:

The purpose and objectives of the lesson:

1. On the basis of the position of metals in the PSCE, to lead students to an understanding of the structural features of their atoms and crystals (metallic chemical bonds and crystalline metal lattice), to study the general physical properties of metals. Review and summarize knowledge about chemical bonding and metal crystal lattice.
2. To develop the ability to analyze, draw conclusions about the structure of atoms based on the position of metals in the PSCE.
3. Develop the ability to master chemical terminology, clearly formulate and express your thoughts.
4. To foster independent thinking in the course of educational activities.
5. To generate interest in the future profession.

Lesson form:

combined lesson with presentation

Methods and techniques:

Story, conversation, video demonstration of the types of crystal lattices of metals, test, drawing up diagrams of the electronic structure of atoms, demonstration of a collection of samples of metals and alloys.

Equipment:

1. Table “Periodic table of chemical elements of D.I. Mendeleev ";
2. Presentation of the lesson on electronic media.
3. Collection of samples of metals and alloys.
4. Projector.
5. Cards with the table "Characteristics of the structure of the atom by position in the PSCE"
   

DURING THE CLASSES

I. Organizing time lesson.

II. Statement and announcement of the topic of the lesson, its goals and objectives.

Slide 1-2

III. Learning new material.

Teacher: Man has used metals since ancient times. Briefly about the history of the use of metals.

1 student message. Slide 3

In the beginning there was a copper age.

By the end of the Stone Age, man discovered the possibility of using metals for the manufacture of tools. The first such metal was copper.

The period of the spread of copper tools is called Chalcolithic or Chalcolithic , which translated from Greek means "copper". Copper was processed using stone tools using the cold forging method. Copper nuggets were turned into products under heavy hammer blows. At the beginning of the Copper Age, only soft tools, jewelry, and household items were made of copper. It was with the discovery of copper and other metals that the profession of a blacksmith began to emerge.

Later, casting appeared, and then people began to add tin or antimony to copper, to make bronze, more durable, strong, fusible.

Student message 2. Slide 3

Bronze - an alloy of copper and tin. The chronological boundaries of the Bronze Age date back to the beginning of the 3rd millennium BC. before the beginning of the 1st millennium BC

Student message 3. Slide 4

The third and final period of the primitive era is characterized by the spread of iron metallurgy and iron tools and marks the Iron Age. In its modern meaning, this term was introduced in the middle of the 9th century by the Danish archaeologist K. Yu. Thomson and soon spread in literature along with the terms “Stone Age” and “Bronze Age”.

Unlike other metals, iron, except for meteorite, is almost never found in its pure form. Scientists assume that the first iron that fell into the hands of man was of meteorite origin, and it is not for nothing that the iron is called the "heavenly stone." The largest meteorite found in Africa, it weighed about sixty tons. And in the ice of Greenland they found an iron meteorite weighing thirty-three tons.

And now the Iron Age continues. Indeed, at present, iron alloys make up almost 90% of all metals and metal alloys.

Teacher.

Gold and silver - precious metals are currently used for the manufacture of jewelry, as well as parts in electronics, aerospace, shipbuilding. Where can these metals be used in shipping? The exceptional importance of metals for the development of society is due, of course, to their unique properties. Name these properties.

Demonstrate to students a collection of metal samples.

Students name such properties of metals as electrical conductivity and thermal conductivity, characteristic metallic luster, plasticity, hardness (except for mercury), etc.

The teacher asks the students a key question: what are the reasons for these properties?

Expected response:properties of substances are due to the structure of molecules and atoms of these substances.

Slide 5. So, metals are a group of substances with common properties.

Demonstration of presentation.

Teacher: Metals are elements of 1-3 groups of main subgroups, and elements of 4-8 groups of secondary subgroups.

Slide 6. Task 1 ... On your own, using PSChE, add in the notebook the representatives of the groups that are metals.

Hearing students' answers selectively.

Teacher: the metals will be the elements located in the lower left corner of the PSCE.

The teacher emphasizes that all elements located below the B - At diagonal, even those with 4 electrons (Ge, Sn, Pb), 5 electrons (Sb, Bi), 6 electrons (Po) on the outer layer, will be metals in PSCE, since they have a large radius.

Thus, 85 of 109 PSCE elements are metals. Slide number 7

Teacher: the position of the element in the PSCE reflects the atomic structure of the element. Using the tables that you received at the beginning of the lesson, we characterize the structure of the sodium atom by its position in the PSCE.
Demonstration of slide 8.

What is a sodium atom? Look at an approximate model of the sodium atom, in which you can see the nucleus and electrons moving in orbits.

Demonstration of Slide 9.Sodium atom model.

Let me remind you how a diagram of the electronic structure of an atom of an element is drawn up.

Demonstration of slide 10.You should have the following diagram of the electronic structure of the sodium atom.

Slide 11. Task 2. Make a diagram of the electronic structure of the calcium and aluminum atom in the notebook yourself, following the example with the sodium atom.

The teacher checks the work in the notebook.

What conclusion can be drawn about the electronic structure of metal atoms?

On the external energy level, 1-3 electrons. We remember that when entering into chemical compounds, atoms strive to restore the full 8-electron shell of the external energy level. For this, metal atoms easily donate 1-3 electrons from the external level, turning into positively charged ions. At the same time, they show restorative properties.

Demonstration of slide 12. Metals Are chemical elements whose atoms donate electrons to the outer (and sometimes pre-outer) electronic layer, turning into positive ions. Metals are reducing agents. This is due to the small number of electrons in the outer layer, the large radius of the atoms, as a result of which these electrons are weakly confined to the nucleus.

Let's consider simple substances - metals.

Demonstration of slide 13.

First, we summarize information about the type of chemical bond formed by metal atoms and the structure of the crystal lattice

1. a relatively small number of electrons simultaneously bind many nuclei, the bond is delocalized;
2. valence electrons move freely over the entire piece of metal, which is generally electrically neutral;
3. the metallic bond does not have directionality and saturation.

Demonstration

Slide 14 " Types of crystal lattices of metals»

Slide 15 Video of the crystal lattice of metals.

The students conclude that in accordance with this particular structure, metals are characterized by general physical properties.

The teacher emphasizes that the physical properties of metals are determined precisely by their structure.

Slide 16 The properties of metals are determined by the structure of their atoms.

a) hardness - all metals except mercury, solids under normal conditions. The mildest are sodium, potassium. They can be cut with a knife; the hardest chrome - scratches glass (demo).

b) density - metals are divided into light (5g / cm) and heavy (more than 5g / cm) (demonstration).

c) fusibility - metals are divided into fusible and refractory (demonstration).

G) electrical conductivity, thermal conductivitymetals due to their structure. Chaotically moving electrons under the action of an electric voltage acquire a directional movement, as a result of which an electric current arises.

With an increase in temperature, the amplitude of the motion of atoms and ions located in the nodes of the crystal lattice increases sharply, and this interferes with the movement of electrons, and the electrical conductivity of metals decreases.

It should be noted that in some non-metals, with an increase in temperature, the electrical conductivity increases, for example, in graphite, while with an increase in temperature, some covalent bonds are destroyed, and the number of freely moving electrons increases.

e) metallic luster- electrons filling the interatomic space reflect light rays, and do not transmit, like glass.

Therefore, all metals in the crystalline state have a metallic luster. For most metals, all rays of the visible part of the spectrum are equally scattered, therefore they have a silvery - White color... Only gold and copper absorb to a large extent short wavelengths and reflect long wavelengths of the light spectrum, therefore they have yellow light. The brightest metals are mercury, silver, palladium. In the powder, all metals, except for AI and Mg, lose their luster and have a black or dark gray color.

f) plasticity ... Mechanical action on a crystal with a metal lattice only causes displacement of atomic layers and is not accompanied by bond breaking, and therefore the metal is characterized by high ductility.

IV. Consolidation of the studied material.

Teacher: we examined the structure and physical properties of metals, their position in the periodic table of chemical elements of D.I. Mendeleev. Now, to consolidate, we suggest performing a test.

Slides 15-16-17.

1) Electronic formula of calcium.

1. a) 1S 2 2S 2 2P 6 3S 1
2. b) 1S 2 2S 2 2P 6 3S 2
3. c) 1S 2 2S 2 2P 6 3S 2 3S 6 4S 1
4. d) 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2

2) Electronic formula 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2 has an atom:

1. a) Na
2. b) Ca
3. c) Сu
4. d) Zn

3) Electrical conductivity, metallic luster, plasticity, density of metals are determined by:

1. a) the mass of metal
2. b) the melting point of metals
3. c) the structure of metal atoms
4. d) the presence of unpaired electrons

4) Metals, when interacting with non-metals, exhibit properties

1. a) oxidative;
2. b) restorative;
3. c) both oxidizing and reducing;
4. d) do not participate in redox reactions;

5) In the periodic table, typical metals are located in:

1. a) upper part;
Vi. Homework.

The structure of metal atoms, their physical properties




Metals make up most of the chemical elements. Each period of the periodic system (except for the 1st) chemical elements begins with metals, and with an increase in the number of the period, they become more and more. If in the 2nd period there are only 2 metals (lithium and beryllium), in the 3rd - 3 (sodium, magnesium, aluminum), then already in the 4th - 13, and in the 7th - 29.

Metal atoms have a similarity in the structure of the outer electron layer, which is formed by a small number of electrons (mostly no more than three).

This statement can be illustrated by the examples of Na, aluminum A1 and zinc Zn. Drawing up diagrams of the structure of atoms, if you wish, you can draw up electronic formulas and give examples of the structure of elements of long periods, for example, zinc.

Due to the fact that the electrons of the outer layer of metal atoms are weakly bound to the nucleus, they can be "given" to other particles, which happens during chemical reactions:



The property of metal atoms to donate electrons is their characteristic chemical property and indicates that the metals exhibit reducing properties.

When characterizing the physical properties of metals, one should note their general properties: electrical conductivity, thermal conductivity, metallic luster, plasticity, which are due to a single type of chemical bond - metal and metal crystal lattice. Their feature is the presence of freely moving shared electrons between ion-atoms located at the sites of the crystal lattice.

When characterizing the chemical properties, it is important to confirm the conclusion that in all reactions metals exhibit the properties of reducing agents, and to illustrate this by writing down the reaction equations. Particular attention should be paid to the interaction of metals with acids and salt solutions; in this case, it is necessary to refer to a number of metal voltages (a number of standard electrode potentials).

Examples of the interaction of metals with simple substances (non-metals):



With salts (Zn in the series of voltages is to the left of Cu): Zn + CuC12 = ZnCl2 + Cu!

Thus, despite the great variety of metals, they all have common physical and chemical properties, which is explained by the similarity in the structure of atoms and the structure of simple substances.

Introduction Metals are simple substances with characteristic properties under ordinary conditions: high electrical conductivity and thermal conductivity, the ability to reflect light well (which determines their brilliance and opacity), the ability to take the desired shape under the influence external forces(plasticity). There is another definition of metals - these are chemical elements characterized by the ability to donate external (valence) electrons. Of all the known chemical elements, about 90 are metals. Most inorganic compounds are metal compounds.

There are several types of metal classification. The clearest is the classification of metals in accordance with their position in the periodic table of chemical elements - chemical classification. If in the "long" version periodic table draw a straight line through the elements boron and astatine, then metals will be located to the left of this line, and non-metals to the right of it. From the point of view of the structure of the atom, metals are subdivided into non-transitional and transitional.

Non-transition metals are located in the main subgroups of the periodic system and are characterized by the fact that in their atoms there is a successive filling of the electronic levels s and p. Intransition metals include 22 elements of the main subgroups a: Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, Ga, In, Tl, Ge, Sn, Pb, Sb, Bi, Po. Transition metals are located in side subgroups and are characterized by the filling of d - or f-electronic levels.

The d-elements include 37 metals of side subgroups b: Cu, Ag, Au, Zn, Cd, Hg, Sc, Y, La, Ac, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo , W, Sg, Mn, Tc, Re, Bh, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Hs, Mt. The f-elements include 14 lanthanides (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Du, Ho, Er, Tm, Yb, Lu) and 14 actinides (Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr). Among the transition metals, there are also rare earth metals (Sc, Y, La and lanthanides), platinum metals (Ru, Rh, Pd, Os, Ir, Pt), transuranic metals (Np and elements with a higher atomic mass). In addition to the chemical, there is also, although not generally accepted, but long established technical classification of metals.

It is not as logical as the chemical one; it is based on one or another practically important feature of a metal. Iron and alloys based on it are classified as ferrous metals, all other metals are classified as nonferrous. There are light (Li, Be, Mg, Ti, etc.) and heavy metals (Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg, Sn, Pb, etc.), as well as groups of refractory (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Re), precious (Ag, Au, platinum metals) and radioactive (U, Th, Np, Pu, etc.) metals.

In geochemistry, scattered (Ga, Ge, Hf, Re, etc.) and rare (Zr, Hf, Nb, Ta, Mo, W, Re, etc.) metals are also distinguished. As can be seen, there are no clear boundaries between the groups. Historical background Despite the fact that the life of human society is impossible without metals, no one knows for sure when and how a person began to use them for the first time.

The most ancient writings that have come down to us tell of primitive workshops in which metal was smelted and products were made from it. This means that man mastered metals earlier than writing. Digging up ancient settlements, archaeologists find tools of labor and hunting, which were used by people in those distant times, knives, axes, arrowheads, needles, fish hooks and much more. The older the settlements, the more crude and primitive were the products of human hands. The most ancient metal products were found during excavations of settlements that existed about 8 thousand years ago.

These were mainly jewelry made of gold and silver, and arrowheads and spearheads made of copper. The Greek word "metallon" originally meant mines, mines, hence the term "metal" originated. In ancient times, it was believed that there were only 7 metals: gold, silver, copper, tin, lead, iron and mercury. This number was correlated with the number of planets known then - the Sun (gold), the Moon (silver), Venus (copper), Jupiter ( tin), Saturn (lead), Mars (iron), Mercury (mercury) (see figure). According to alchemical concepts, metals originated in the bowels of the earth under the influence of the rays of the planets and gradually improved, turning into gold.

Man first mastered native metals - gold, silver, mercury. The first artificially obtained metal was copper, then he managed to master the production of an alloy of copper with salt - bronze and only later - iron.

In 1556, a book by the German metallurgist G. Agricola "On mining and metallurgy" was published in Germany - the first detailed guide to the production of metals that has come down to us. True, at that time, lead, tin and bismuth were still considered varieties of the same metal. In 1789, the French chemist A. Lavoisier, in his manual on chemistry, gave a list of simple substances, which included all the metals known then - antimony, silver, bismuth, cobalt , tin, iron, manganese, nickel, gold, platinum, lead, tungsten, and zinc. With the development of methods of chemical research, the number of known metals began to increase rapidly. In the 18th century. 14 metals were discovered, 19 in 38, 20 in 25 metals.

In the first half of the 19th century. satellites of platinum were discovered, alkali and alkaline earth metals were obtained by electrolysis. In the middle of the century, cesium, rubidium, thallium and indium were discovered by the method of spectral analysis. The existence of metals predicted by D. I. Mendeleev on the basis of his periodic law(these are gallium, scandium and germanium). The discovery of radioactivity at the end of the 19th century. entailed a search for radioactive metals.

Finally, by the method of nuclear transformations in the middle of the 20th century. radioactive metals that do not exist in nature were obtained, in particular transuranium elements. Physical and chemical properties of metals. All metals are solids (except for mercury, which is liquid under normal conditions), they differ from non-metals in a special type of bond (metallic bond). Valence electrons are weakly bound to a specific atom, and inside each metal there is a so-called electron gas. Most metals have a crystalline structure, and the metal can be thought of as a "rigid" crystal lattice of positive ions (cations). These electrons can more or less move around the metal.

They compensate for the repulsive forces between the cations and, thus, bind them into a compact body. All metals have high electrical conductivity (that is, they are conductors, as opposed to non-metallic dielectrics), especially copper, silver, gold, mercury and aluminum; the thermal conductivity of metals is also high.

A distinctive feature of many metals is their ductility (malleability), as a result of which they can be rolled into thin sheets (foil) and drawn into a wire (tin, aluminum, etc.), but there are also quite brittle metals (zinc, antimony, bismuth). In industry, not pure metals are often used, but their mixtures, called alloys.

In an alloy, the properties of one component usually complement the properties of the other. So, copper has a low hardness and is of little use for the manufacture of machine parts, while copper-zinc alloys, called brass, are already quite hard and widely used in mechanical engineering. Aluminum has good ductility and sufficient lightness (low density), but is too soft. On its basis, an alloy of ayuralumin (duralumin) is prepared, containing copper, magnesium and manganese.

Duralumin, without losing the properties of its aluminum, acquires a high hardness and therefore is used in aviation technology. Alloys of iron with carbon (and additives of other metals) are well-known cast iron and steel. Metals vary greatly in density: for lithium it is almost half that of water (0.53 g / cm3), and for osmium it is more than 20 times higher (22.61 g / cm3). Metals also differ in hardness. The softest - alkali metals, they are easily cut with a knife; the hardest metal - chrome - cuts glass.

The difference in the melting temperatures of metals is great: mercury is a liquid under normal conditions, cesium and gallium melt at the temperature of a human body, and the most refractory metal, tungsten, has a melting point of 3380 ° C. Metals with a melting point above 1000 ° C are referred to as refractory metals, below - to low-melting ones. At high temperatures, metals are capable of emitting electrons, which is used in electronics and thermoelectric generators for direct conversion of thermal energy into electrical energy.

Iron, cobalt, nickel and gadolinium, after placing them in a magnetic field, are able to constantly maintain a state of magnetization. Metals also have some chemical properties. Metal atoms relatively easily donate valence electrons and transform into positively charged ions. Therefore, metals are reducing agents. This, in fact, is their main and most general chemical property. Obviously, metals as reducing agents will enter into reactions with various oxidants, among which there may be simple substances, acids, salts of less active metals and some other compounds.

Compounds of metals with halogens are called halides, with sulfur - sulfides, with nitrogen - nitrides, with phosphorus - phosphides, with carbon - carbides, with silicon - silicides, with boron - borides, with hydrogen - hydrides, etc. Many of these compounds found important applications in new technology. For example, metal borides are used in radio electronics, as well as in nuclear technology as materials to regulate neutron radiation and protect against it. Under the action of concentrated oxidizing acids, a stable oxide film is also formed on some metals.

This phenomenon is called passivation. Thus, in concentrated sulfuric acid such metals as Be, Bi, Co, Fe, Mg, and Nb are passivated (and do not react with it), and in concentrated nitric acid - metals Al, Be, Bi, Co , Cr, Fe, Nb, Ni, Pb, Th and U. The more to the left the metal is located in this row, the more reducing properties it possesses, that is, it oxidizes more easily and passes in the form of a cation into a solution, but it is more difficult to recover from a cation into a free state.

One non-metal, hydrogen, is placed in a series of voltages, since this makes it possible to determine whether a given metal will react with acids - non-oxidizing agents in an aqueous solution (more precisely, it will be oxidized by hydrogen cations H +). For example, zinc reacts with hydrochloric acid, since in the series of voltages it stands to the left (up to) hydrogen.

On the contrary, silver is not transferred into solution by hydrochloric acid, since it stands in the series of voltages to the right (after) of hydrogen. Metals behave similarly in dilute sulfuric acid. Metals in the series of stresses after hydrogen are called noble (Ag, Pt, Au, etc.) contact with water and under the influence of oxygen dissolved in it (oxygen corrosion). For example, corrosion of iron products in water is widely known. Particularly corrosive can be the place of contact of two dissimilar metals - contact corrosion.

A galvanic pair arises between one metal, such as Fe, and another metal, such as Sn or Cu, placed in water. The flow of electrons goes from the more active metal, which is to the left in the series of voltages (Fe), to the less active metal (Sn, Cu), and the more active metal is destroyed (corroded). It is because of this that the tinned surface of tin cans (tin-coated iron) rusts when stored in a humid atmosphere and carelessly handling them (iron quickly collapses after the appearance of at least a small scratch that allows iron to come into contact with moisture). On the contrary, the galvanized surface of an iron bucket does not rust for a long time, because even in the presence of scratches, it is not iron that corrodes, but zinc (a more active metal than iron). Corrosion resistance for a given metal increases when it is coated with a more active metal or when they are fused; for example, plating iron with chromium or making iron-chromium alloys eliminates the corrosion of iron.

Chromium-plated iron and chrome-containing steels (stainless steels) have high corrosion resistance.

General methods of obtaining metals: - electrometallurgy, ie, obtaining metals by electrolysis of melts (for the most active metals) or solutions of their salts; - pyrometallurgy, i.e. the recovery of metals from their ores at high temperatures (for example, the production of iron using a blast furnace process); - hydrometallurgy, i.e. the separation of metals from solutions of their salts with more active metals (for example, the production of copper from a CuSO4 solution by displacement by zinc, iron or aluminum). In nature, metals are sometimes found in free form, for example, native mercury, silver and gold, and more often in the form of compounds (metal ores). The most active metals, of course, are present in the earth's crust only in bound form. Lithium. Lithium (from the Greek. Lithos - stone), Li, a chemical element of subgroup Ia of the periodic system; atomic number 3, atomic mass 6, 941; refers to alkali metals.

It is found in more than 150 minerals, of which about 30 are actually lithium. The main minerals are spodumene LiAl, lepidolite KLi1.5 Al1.5 (F, 0H) 2 and petalite (LiNa). The composition of these minerals is complex, many of them belong to the class of aluminosilicates, very widespread in the earth's crust.

Promising sources of raw materials for lithium production are brines (brine) of saline deposits and The groundwater... The largest deposits of lithium compounds are found in Canada, the USA, Chile, Zimbabwe, Brazil, Namibia and Russia. It is interesting that the mineral spodumene occurs naturally in the form of large crystals weighing several tons. At the Etta mine in the USA, they found a crystal in the shape of a needle 16 m long and weighing 100 tons. The first information about lithium dates back to 1817. The Swedish chemist A. Arfvedson, while analyzing the mineral petalite, discovered an unknown alkali in it. Arfvedson's teacher J. Berzelius gave it the name "lithion" (from the Greek liteo-stone), because, unlike potassium and sodium hydroxides, which were obtained from plant ash, a new alkali was found in the mineral. He also called the metal, which is the "base" of this alkali, lithium. In 1818 the English chemist and physicist G. Davy obtained lithium by electrolysis of LiOH hydroxide. Properties.

Lithium is a silvery white metal; t. pl. 180.54 ° C, bp 1340 "C; the lightest of all metals, its density is 0.534 g / cm - it is 5 times lighter than aluminum and almost twice lighter than water. Lithium is soft and ductile.

Lithium compounds give the flame a beautiful carmine red color. This very sensitive method is used in qualitative analysis to detect lithium. The configuration of the outer electron layer of a lithium atom is 2s1 (s-element). In compounds, it exhibits an oxidation state of +1. Lithium is the first in the electrochemical series of voltages and displaces hydrogen not only from acids, but also from water. However, many chemical reactions in lithium are less vigorous than other alkali metals. Lithium practically does not react with air components in the complete absence of moisture at room temperature.

When heated in air above 200 ° C, it forms oxide Li2O as the main product (only traces of Li2O2 peroxide are present). In humid air it produces mainly Li3N nitride, with air humidity over 80% - LiOH hydroxide and Li2CO3 carbonate. Lithium nitride can also be obtained by heating a metal in a stream of nitrogen (lithium is one of the few elements that directly combine with nitrogen): 6Li + N2 = 2Li3N Lithium easily fuses with almost all metals and is readily soluble in mercury.

It combines directly with halogens (with iodine when heated). At 500 ° C, it reacts with hydrogen, forming LiH hydride, when interacting with water - LiOH hydroxide, with dilute acids - lithium salts, with ammonia - LiNH2 amide, for example: 2Li + H2 = 2LiH 2Li + 2H2O = 2LiOH + H2 2Li + 2HF = 2LiF + H2 2Li + 2NH3 = 2LiNH2 + H2 LiH hydride - colorless crystals; used in various fields of chemistry as a reducing agent.

When interacting with water, it releases a large amount of hydrogen (from 1 kg of LiH, 2820 liters of H2 are obtained): LiH + H2O = LiOH + H2 This makes it possible to use LiH as a source of hydrogen for filling balloons and rescue equipment (inflatable boats, belts, etc.), and as well as a kind of "warehouse" for storing and transporting flammable hydrogen (in this case, it is necessary to protect LiH from the slightest traces of moisture). Mixed lithium hydrides are widely used in organic synthesis, for example, lithium aluminum hydride LiAlH4, a selective reducing agent.

It is obtained by the interaction of LiH with aluminum chloride A1C13. LiOH hydroxide is a strong base (alkali), its aqueous solutions destroy glass and porcelain; Nickel, silver and gold are resistant to it.

LiOH is used as an additive to the electrolyte of alkaline batteries, which increases their service life by 2-3 times and their capacity by 20%. On the basis of LiOH and organic acids (especially stearic and palmitic acids), frost and heat-resistant greases (lithols) are produced to protect metals from corrosion in the temperature range from -40 to +130 "C. Lithium hydroxide is also used as a carbon dioxide absorber in gas masks, submarines, airplanes and spaceships.

Receiving and applying. The raw materials for producing lithium are its salts, which are extracted from minerals. Depending on the composition, minerals are decomposed with sulfuric acid H2SO4 (acid method) or by sintering with calcium oxide CaO and its carbonate CaCO3 (alkaline method), with potassium sulfate K2SO4 (salt method), with calcium carbonate and its chloride CaCl (alkaline-salt method). With the acid method, a solution of Li2SO4 sulfate is obtained [the latter is freed from impurities by treatment with calcium hydroxide Ca (OH) 2 and soda Na2Co3]. The cake formed by other methods of decomposition of minerals is leached with water; at the same time, with the alkaline method, LiOH passes into the solution, with the salt method - Li 2SO4, with the alkaline-salt method - LiCl. All these methods, except for alkaline, provide for the production of the finished product in the form of Li2CO3 carbonate. which is used directly or as a source for the synthesis of other lithium compounds.

Lithium metal is obtained by electrolysis of a molten mixture of LiCl and potassium chloride KCl or barium chloride BaCl2 with further purification from impurities. The interest in lithium is enormous.

This is primarily due to the fact that it is a source of industrial production of tritium (heavy hydrogen nuclide), which is the main component of the hydrogen bomb and the main fuel for thermonuclear reactors. The thermonuclear reaction is carried out between the 6Li nuclide and neutrons (neutral particles with a mass number of 1 ); reaction products - tritium 3H and helium 4He: 63Li + 10n = 31 H + 42He A large amount of lithium is used in metallurgy. Magnesium alloy with 10% lithium is stronger and lighter than magnesium itself.

Alloys of aluminum and lithium - scleron and aeron, containing only 0.1% lithium, in addition to being light, have high strength, ductility, and increased resistance to corrosion; they are used in aviation. The addition of 0.04% lithium to lead-calcium bearing alloys increases their hardness and reduces the coefficient of friction. Lithium halides and carbonate are used in the production of optical, acid-resistant and other special glasses, as well as heat-resistant porcelain and ceramics, various glazes and enamels.

Small lithium crumbs cause chemical burns to damp skin and eyes. Lithium salts irritate the skin. When working with lithium hydroxide, follow the same precautions as when working with sodium and potassium hydroxides. Sodium.Sodium (from Arab, natrun, Greek nitrone - natural soda, chemical element of subgroup Ia of the periodic system; atomic number 11, atomic mass 22.98977; refers to alkali metals.

It occurs naturally in the form of one stable nuclide 23 Na. Even in ancient times, sodium compounds were known - table salt (sodium chloride) NaCl, caustic alkali (sodium hydroxide) NaOH and soda (sodium carbonate) Na2CO3. The last substance the ancient Greeks called "nitron"; hence the modern name of the metal - "sodium". However, in Great Britain, the USA, Italy, France, the word sodium is preserved (from the Spanish word "soda", which has the same meaning as in Russian). For the first time, the receipt of sodium (and potassium) was reported by the English chemist and physicist G. Davy at a meeting of the Royal Society in London in 1807. electric current caustic alkalis KOH and NaOH and isolate previously unknown metals with extraordinary properties.

These metals oxidized very quickly in air, and floated on the surface of the water, releasing hydrogen from it. Prevalence in nature Sodium is one of the most abundant elements in nature.

Its content in the earth's crust is 2.64% by weight. In the hydrosphere, it is contained in the form of soluble salts in an amount of about 2.9% (with a total salt concentration in seawater of 3.5-3.7%). The presence of sodium has been established in the solar atmosphere and interstellar space. nature, sodium is found only in the form of salts. The most important minerals - halite (rock salt) NaCl, mirabilite (Glauber's salt) Na2SO4 * 10H2O, thenardite Na2SO4, Chelyan nitrate NaNO3, natural silicates, such as albite Na, nepheline Na Russia is extremely rich in deposits of rock salt ( for example, Solikamsk, Usolye-Sibirskoye, etc.), large deposits of the mineral trona in Siberia.

Properties. Sodium is a silvery-white low-melting metal, m.p. 97.86 ° C, bp. 883.15 ° C. It is one of the lightest metals - it is lighter than water (density 0.99 g / cm3 at 19.7 ° C). Sodium and its compounds color the burner flame yellow. This reaction is so sensitive that it reveals the presence of the slightest trace of sodium everywhere (for example, in room or street dust). Sodium is one of the most active elements in the periodic table.

The outer electron layer of the sodium atom contains one electron (configuration 3s1, sodium - s-element). Sodium easily gives up its only valence electron and therefore always exhibits an oxidation state of +1 in its compounds. In air, sodium is actively oxidized, forming, depending on the conditions, the oxide Na2O or peroxide Na2O2. Therefore, sodium is stored under a layer of kerosene or mineral oil. Reacts vigorously with water, displacing hydrogen: 2Na + Н20 = 2NaОН + Н2 Such a reaction occurs even with ice at a temperature of -80 ° С, and with warm water or at the contact surface, it goes with an explosion (no wonder they say: “You don’t want to become a freak - throw the sodium into the water "). Sodium directly reacts with all non-metals: at 200 ° C it begins to absorb hydrogen, forming a very hygroscopic hydride NaH; with nitrogen in an electric discharge gives the nitride Na3N or azide NaN3; ignites in an atmosphere of fluorine; in chlorine burns at a temperature; reacts with bromine only when heated: 2Na + Н2 = 2NaН 6Na + N2 = 2Na3N or 2Na + 3Na2 = 2NaN3 2Na + С12 = 2NaСl At 800-900 ° С sodium combines with carbon, forming carbide Na2C2; when rubbed with sulfur gives sulfide Na2S and a mixture of polysulfides (Na2S3 and Na2S4) Sodium easily dissolves in liquid ammonia, the resulting blue solution has metallic conductivity, with gaseous ammonia at 300-400 "C or in the presence of a catalyst when cooled to -30 C gives amide NaNH2 Sodium forms compounds with other metals (intermetallic compounds), for example with silver, gold, cadmium, lead, potassium and some others.

With mercury, it gives amalgams NaHg2, NaHg4, etc. The most important are liquid amalgams, which are formed with the gradual introduction of sodium into mercury under a layer of kerosene or mineral oil.

Sodium forms salts with dilute acids. Receiving and using.

The main method for producing sodium is electrolysis of molten table salt. In this case, chlorine is released at the anode, and sodium at the cathode.

To reduce the melting point of the electrolyte, other salts are added to table salt: KCl, NaF, CaCl2. Electrolysis is carried out in electrolysers with a diaphragm; anodes are made of graphite, cathodes are made of copper or iron. Sodium can be obtained by electrolysis of molten hydroxide NaOH, and small amounts by decomposition of azide NaN3. Metallic sodium is used to reduce pure metals from their compounds - potassium (from KOH), titanium (from TiCl4), etc. Sodium-potassium alloy is a coolant for nuclear reactors, since alkali metals poorly absorb neutrons and therefore do not interfere with the fission of uranium nuclei.

Sodium vapor, which has a bright yellow glow, is used to fill gas-discharge lamps used to illuminate highways, marinas, train stations, etc. Sodium is used in medicine: the artificially obtained nuclide 24Na is used for the radiological treatment of certain forms of leukemia and for diagnostic purposes. The use of sodium compounds is much more extensive.

Na2O2 peroxide - colorless crystals, yellow technical product. When heated to 311-400 ° C, it begins to release oxygen, and at 540 ° C it rapidly decomposes. It is a strong oxidizing agent, due to which it is used for bleaching fabrics and other materials. It absorbs CO2 in the air ”, releasing oxygen and forming carbonate 2Na2O2 + 2CO2 = 2Na2Co3 + O2). This property is based on the use of Na2O2 for air regeneration in enclosed spaces and breathing apparatus of an insulating type (submarines, insulating gas masks, etc.). NaOH hydroxide; outdated name - caustic soda, technical name - caustic soda (from Latin caustic - caustic, burning); one of the strongest foundations.

The technical product, in addition to NaOH, contains impurities (up to 3% Na2CO3 and up to 1.5% NaCl). A large amount of NaOH is used for the preparation of electrolytes for alkaline batteries, for the production of paper, soap, paints, cellulose, and is used for refining petroleum and oils.

Of sodium salts, chromate Na2CrO4 is used - in the production of dyes, as a mordant for dyeing fabrics and a tanning agent in the tanning industry; sulfite Na2SO3 - a component of fixers and developers in photography; hydrosulfite NaHSO3 - bleach of fabrics, natural fibers, used for canning fruits, vegetables and vegetable feed; thiosulfate Na2S2O3 - to remove chlorine during bleaching of fabrics, as a fixative in photography, an antidote for poisoning with compounds of mercury, arsenic and other anti-inflammatory agent; chlorate NaClO3 - an oxidizing agent in various pyrotechnic compositions; triphosphate Na5P3O10 -additive to synthetic detergents for water softening. Sodium, NaOH and its solutions cause severe burns to the skin and mucous membranes.

Potassium. By appearance and potassium is similar to sodium, but more reactive. Reacts vigorously with water and ignites hydrogen.

Burns in air, forming orange superoxide KO2. At room temperature, it reacts with halogens, with moderate heating - with hydrogen, sulfur. In humid air, it quickly becomes covered with a KOH layer. Potassium is stored under a layer of gasoline or kerosene. The most practical applications are potassium compounds - KOH hydroxide, KNO3 nitrate and K2CO3 carbonate. Potassium hydroxide KOH (technical name - caustic potassium) - white crystals that spread out in humid air and absorb carbon dioxide (K2CO3 and KHCO3 are formed). It dissolves very well in water with a high exo-effect. The aqueous solution is highly alkaline.

Potassium hydroxide is produced by electrolysis of a KCl solution (similar to the production of NaOH). The starting potassium chloride KCl is obtained from natural raw materials (minerals sylvin KCl and carnallite KMgC13 6H20). KOH is used for the synthesis of various potassium salts, liquid soap, dyes, as an electrolyte in batteries. Potassium nitrate KNO3 (potassium nitrate mineral) - white crystals, very bitter in taste, low-melting (melting point = 339 ° C). Let's well dissolve in water (hydrolysis is absent). When heated above the melting point, it decomposes into potassium nitrite KNO2 and oxygen O2, exhibits strong oxidizing properties.

Sulfur and charcoal ignite upon contact with the KNO3 melt, and the C + S mixture explodes (combustion of "black powder"): 2КNO3 + ЗС (coal) + S = N2 + 3CO2 + K2S Potassium nitrate is used in the production of glass and mineral fertilizers.

Potassium carbonate K2CO3 (technical name - potash) is a white hygroscopic powder. It dissolves very well in water, strongly hydrolyzes by anion and creates an alkaline environment in solution. It is used in the manufacture of glass and soap. Obtaining К2СO3 is based on the reactions: К2SO4 + Са (ОН) 2 + 2СO = 2К (НСОО) + СаSO4 2К (НСОО) + O2 = К2С03 + Н20 + С02 Potassium sulfate from natural raw materials (minerals kainite КМg (SO4) Сl ЗН20 and shonite K2Mg (SO4) 2 * 6H20) is heated with slaked lime Ca (OH) 2 in a CO atmosphere (under a pressure of 15 atm), potassium formate K (HCOO) is obtained, which is calcined in a stream of air.

Potassium is a vital element for plants and animals. Potash fertilizers are potassium salts, both natural and products of their processing (KCl, K2SO4, KNO3); the content of potassium salts in plant ash is high. Potassium is the ninth most abundant element in the earth's crust. It is contained only in bound form in minerals, sea water (up to 0.38 g of K + ions in 1 liter), plants and living organisms (inside cells). The human body contains = 175 g of potassium, daily requirement reaches ~ 4g. The radioactive isotope 40K (an admixture to the predominant stable isotope 39K) decays very slowly (half-life 1 109 years), it, along with isotopes 238U and 232Тh, makes a large contribution to the geothermal reserve of our planet (internal heat of the earth's interior). Copper. From (lat. Cuprum), Cu, chemical element of subgroup 16 of the periodic system; atomic number 29, atomic mass 63.546 refers to transition metals. Natural copper is a mixture of nuclides with massive numbers 63 (69.1%) and 65 (30.9%). Prevalence in nature.

The average copper content in the earth's crust is 4.7-10 ~ 3% by weight.

In the earth's crust, copper is found both in the form of nuggets and in the form of various minerals. Copper nuggets, sometimes of considerable size, are covered with a green or blue coating and are unusually heavy in comparison with stone; the largest nugget weighing about 420 tons was found in the United States in the Great Lakes region (figure). The overwhelming majority of copper is present in rocks in the form of compounds.

More than 250 copper minerals are known. Of industrial importance are: chalcopyrite (copper pyrite) CuFeS2, covellite (copper indigo) Cu2S, chalcosine (copper luster) Cu2S, cuprite Cu2O, malachite CuCO3 * Cu (OH) 2 and azurite 2CuCO3 * Cu (OH) 2. Almost all copper minerals are bright and beautifully colored, for example, chalcopyrite casts gold, copper luster has a bluish-steel color, azurite is deep blue with a glassy luster, and pieces of covellite are cast in all the colors of the rainbow.

Many of the copper minerals are semi-precious stones and gems; Malachite and turquoise CuA16 (PO4) 4 (OH) 8 * 5H2O are highly valued. The largest deposits of copper ores are located in the Northern and South America(mainly in the USA, Canada, Chile, Peru, Mexico), Africa (Zambia, South Africa), Asia (Iran, Philippines, Japan). In Russia, there are deposits of copper ores in the Urals and Altai. Copper ores are usually polymetallic: in addition to copper, they contain Fe, Zn, Pb, Sn, Ni, Mo, Au, Ag, Se, platinum metals, etc. Historical background.

Copper has been known since time immemorial and is included in the "magnificent seven" of the most ancient metals used by mankind: gold, silver, copper, iron, tin, lead and mercury. According to archaeological data, copper was known to people for 6,000 years ago. It turned out to be the first metal that replaced stone in primitive tools for ancient man. This was the beginning of the so-called. Copper Age, which lasted for about two millennia.

They forged from copper, and then smelted axes, knives, clubs, household items. According to legend, the ancient blacksmith god Hephaestus forged a shield of pure copper for the invincible Achilles. The stones for the 147-meter pyramid of Cheops were also mined and hewn with a copper tool. The ancient Romans exported copper ore from the island of Cyprus, hence the Latin name for copper - "cuprum". The Russian name "copper", apparently, is associated with the word "smida", which in ancient times meant "metal". Ores mined in the Sinai Peninsula sometimes contained ores with an admixture of tin, which led to the discovery of an alloy of copper with tin - bronze.

Bronze turned out to be more fusible and harder than copper itself. The discovery of bronze marked the beginning of a long Bronze Age (4th - 1st millennium BC). Properties. Copper is a red metal. 1083 "C, bp 2567 ° C, density 8.92 g / cm. This is a ductile malleable metal, it is possible to roll sheets of it 5 times thinner than tissue paper.

Copper reflects light well, perfectly conducts heat and electricity, second only to silver. The configuration of the outer electron layers of the copper atom is 3d104s1 (d-element). Although copper and alkali metals are in the same group I, their behavior and properties are very different. Copper is similar to alkali metals only by the ability to form monovalent cations. During the formation of compounds, a copper atom can lose not only the outer s-electron, but one or two d-electrons of the previous layer, thus exhibiting a higher oxidation state.

For copper, the oxidation state +2 is more typical than +1. Metallic copper is inactive, stable in dry and clean air. In humid air containing CO2, a greenish Cu (OH) 2 * CuCO3 film called patina forms on its surface. Patina gives products made of copper and its alloys a beautiful "antique" look; a continuous patina coating, in addition, protects the metal from further destruction. When copper is heated in pure and dry oxygen, black oxide CuO is formed; heating above 375 ° C leads to the red oxide Cu2O. At normal temperatures, copper oxides are stable in air. In the series of voltages, copper is to the right of hydrogen, and therefore it does not displace hydrogen from water and in anoxic acids it does not. Copper can dissolve in acids only when it is simultaneously oxidized, for example, in nitric acid or concentrated sulfuric acid: 3Cu + 8HNO3 = 3Cu (NO3) 2 + 2NO + 4H2O Cu + 2H2S04 = CuSO4 + SO2 + 2H2O Fluorine, chlorine and bromine react with copper , forming the corresponding dihalides, for example: Cu + Cl2 = CuCl2 Interaction of heated copper powder with iodine produces Cu (I) iodide, or copper monoiodide: 2Cu + I2 = 2CuI Copper burns in sulfur vapor, forming CuS monosulfide. It does not interact with hydrogen under normal conditions.

However, if copper samples contain trace impurities of Cu2O oxide, then in an atmosphere containing hydrogen, methane or carbon monoxide, copper oxide is reduced to metal: Cu2O + H2 = 2Cu + H2O Cu2O + CO = 2Cu + CO2 Emitted water and CO2 vapors cause cracks. which sharply worsens the mechanical properties of the metal ("hydrogen disease"). Monovalent copper salts - CuCl chloride, Cu2SO3 sulfite, Cu2S sulfide, and others - are usually poorly soluble in water. For bivalent copper, there are salts of almost all known acids; the most important of them are СuSO4 sulfate, СuСl2 chloride, Cu (NO3) 2 nitrate. All of them dissolve well in water, and when released from it form crystalline hydrates, for example, CuCl2 * 2H2O, Cu (NO3) 2 * 6H2O, Cu804-5H20. The color of the salts is from green to blue, since the Cu ion in water is hydrated and is in the form of a blue aqua ion [Cu (H2O) 6] 2+, which determines the color of solutions of divalent copper salts. One of the most important copper salts - sulfate - is obtained by dissolving the metal in heated dilute sulfuric acid while blowing air: 2Cu + 2H2SO4 + O2 = 2CuSO4 + 2H2O Anhydrous sulfate is colorless; adding water, it turns into copper sulfate CuSO4-5H2O - azure-blue transparent crystals.

Due to the property of copper sulfate to change color when moistened, it is used to detect traces of water in alcohols, ethers, gasolines, etc. When a bivalent copper salt interacts with alkali, a blue bulk precipitate is formed - Cu (OH) 2 hydroxide. It is amphoteric: in concentrated alkali it dissolves to form a salt in which copper is in the form of an anion, for example: Cu (OH) 2 + 2KOH = K2 [Cu (OH) 4] Unlike alkali metals, copper is characterized by a tendency to complex formation - Cu and Cu2 + ions in water can form complex ions with anions (Сl СN-), neutral molecules (NH3) and some organic compounds.

These complexes are usually brightly colored and readily soluble in water. Receiving and applying.

Back in the 19th century. copper was smelted from ores containing at least 15% metal.

Currently, rich copper ores are practically depleted, so copper Ch. arr. are obtained from sulfide ores containing only 1-7% copper. Smelting metal is a long and multi-stage process. After the flotation treatment of the original ore, the concentrate containing iron and copper sulfides is placed in reflex copper smelting furnaces heated to 1200 ° C. The concentrate melts, forming the so-called. matte containing molten copper, iron and sulfur, as well as solid silicate slags that float to the surface.

The smelted matte contains about 30% copper in the form of CuS, the rest is iron sulfide and sulfur. The next stage is the transformation of the matte into the so-called. blister copper, which is carried out in horizontal converter furnaces blown with oxygen.

FeS is oxidized first; quartz is added to the converter to bind the resulting iron oxide, thus forming an easily detachable silicate slag. Then CuS is oxidized, turning into metallic copper, and SO2 is released: CuS + O2 = Cu + SO2 After removing SO2 by air, the blister copper remaining in the converter, containing 97-99% copper, is poured into molds and then subjected to electrolytic cleaning.

For this purpose, billets of blister copper in the form of thick boards are suspended in electrolysis baths containing a solution of copper sulfate with the addition of H2SO4. Thin sheets of pure copper are also suspended in the same baths. They serve as cathodes, and blister copper castings as anodes. During the passage of current, copper dissolves at the anode, and its release occurs at the cathode: Cu - 2e = Cu2 + Cu2 + + 2e = Cu Impurities, including silver, gold, platinum, fall to the bottom of the bath in the form of a silty mass (sludge). The separation of precious metals from the sludge usually pays for this entire energy-intensive process.

After such refining, the resulting metal contains 98-99% copper. Copper has long been used in construction: the ancient Egyptians built copper water pipes; the roofs of medieval castles and churches were covered with copper sheets, for example the famous royal castle in Elsinore (Denmark) was covered with roofing copper.

Coins and jewelry were made from copper.

Due to its low electrical resistance, copper is the main metal in electrical engineering: more than half of all copper produced goes to the production of electrical wires for high-voltage transmissions and low-current cables. Even insignificant impurities in copper lead to an increase in its electrical resistance and large losses of electricity. High thermal conductivity and corrosion resistance make it possible to manufacture parts of heat exchangers, refrigerators, vacuum apparatus, pipelines for pumping oils and fuels, etc. from copper. Copper is also widely used in electroplating when applying protective coatings for steel products.

So, for example, when nickel plating or chrome plating of steel objects, copper is preliminarily deposited on them; in this case, the protective coating lasts longer and more efficiently. Copper is also used in electroforming (i.e. when replicating products by obtaining a mirror image), for example, in the manufacture of metal matrices for printing banknotes, reproducing sculptured products.

A significant amount of copper is consumed in the manufacture of alloys, which it forms with many metals. The main copper alloys are generally divided into three groups: bronzes (alloys with tin and other metals other than zinc and nickel), brass (alloys with zinc), and copper-nickel alloys. There are separate articles on bronzes and brasses in the encyclopedia. The most famous copper-nickel alloys are cupronickel, nickel silver, constantan, manganin; they all contain up to 30-40% nickel and various alloying additives.

These alloys are used in shipbuilding, for the manufacture of parts operating at elevated temperatures, in electrical appliances, as well as for household metal products instead of silver (cutlery). Copper compounds have found and are finding various applications. Bivalent copper oxide and sulfate are used to make certain types of artificial fibers and to obtain other copper compounds; CuO and Cu2O are used for the production of glass and enamels; Cu (NO3) 2 - for calico printing; СuСl2 - a component of mineral paints, a catalyst.

Mineral paints containing copper have been known since ancient times; Thus, an analysis of the ancient frescoes of Pompeii and wall painting in Russia showed that the composition of the paints included the basic copper acetate Cu (OH) 2 * (CH3COO) 2Cu2, it was it that served as a bright green paint, called in Russia yar-copperhead. belongs to the so-called. bioelements necessary for the normal development of plants and animals.

In the absence or lack of copper in plant tissues, the chlorophyll content decreases, the leaves turn yellow, the plants cease to bear fruit and may die. Therefore, many copper salts are part of copper fertilizers, such as copper sulfate, copper-potassium fertilizers (copper sulfate mixed with KSD). Copper salts, in addition, are used to combat plant diseases. For more than a hundred years, Bordeaux liquid containing basic copper sulfate [Cu (OH) 2] 3CuSO4 has been used for this; get it by the reaction: 4СuSO4 + ЗСа (ОН) 2 = СuSO4 * ЗСu (ОН) 2 + ЗСаSО4 The gelatinous sediment of this salt covers the leaves well and stays on them for a long time, protecting the plant.

Cu2O, copper chloroxide 3Cu (OH) 2 * CuCl2, as well as copper phosphate, borate and arsenate have a similar property. In the human body, copper is a part of some enzymes and is involved in the processes of hematopoiesis and enzymatic oxidation; the average copper content in human blood is about 0.001 mg / l. In the organisms of lower animals, copper is much higher, for example, hemocyanin - the blood pigment of mollusks and crustaceans - contains up to 0.26% copper. The average copper content in living organisms is 2-10-4% by weight.

For humans, copper compounds are mostly toxic. Despite the fact that copper is a part of some pharmaceutical preparations, ingestion of it in the stomach with water or food in large quantities can cause severe poisoning. People who work for a long time in the smelting of copper and its alloys often fall ill with "copper fever" - the temperature rises, there are pains in the stomach area, the vital activity of the lungs decreases. If copper salts have entered the stomach, before the arrival of the doctor, it is urgent to rinse it and take a diuretic.

Conclusion. Metals serve as the main structural material in mechanical engineering and instrument making. All of them have common so-called metallic properties, but each element manifests them in accordance with its position in the periodic system of D. I. Mendeleev, i.e., in accordance with the structural features of his atom.

Metals actively interact with elementary oxidants with high electronegativity (halogens, oxygen, sulfur, etc.) and therefore, when considering general properties of metallic elements, it is necessary to take into account their chemical activity in relation to non-metals, the types of their compounds and the forms of chemical bonds, since this determines not only the metallurgical processes during their production, but also the operability of metals under operating conditions.

Today, when the economy is developing at a rapid pace, there is a need for prefabricated buildings that do not require significant capital investments. This is mainly needed for the construction of shopping pavilions, entertainment centers, warehouses. With the use of metal structures, such structures can now not only be easily and quickly erected, but also disassembled with the same ease when the rental period ends or for moving to another place. Moreover, it is not difficult to bring communications, heating, light into such easily erected buildings. Buildings made of metal structures withstand the harsh conditions of nature not only in terms of temperature conditions, but also, which is important in terms of seismological activity, where it is not easy and not safe to erect brick structures.

The range of metal structures offered by the industry today is easily transportable and can be lifted by any cranes. The connection and installation of such structures can be carried out both with bolts and by welding.

The emergence of lightweight metal structures, which are manufactured and supplied in a complex manner, play a large positive role in the construction of public buildings in comparison with the construction of buildings made of reinforced concrete, and significantly reduces the time required to complete the work. 1. Khomchenko G.P. Chemistry manual for university applicants. - 3rd edition - M .: New Wave Publishing House LLC, ONIX Publishing House CJSC, 1999 464 p. 2. A.S. Egorova.

Chemistry. A guide for applicants to universities - 2nd edition - Rostov n / a: publishing house "Phoenix", 1999. - 768 p. 3. Frolov V.V. Chemistry: Textbook for special mechanical engineering universities. - 3rd ed. Rev. and add. - M .: Higher school, 1986 543 p. 4. Lidin R.A. Chemistry. For high school students and those entering universities: Theoretical foundations. Questions. Tasks.Tests: Textbook. Manual / 2nd ed stereotype. - M .: Bustard, 2002 .-- 576 p. 5. Yu.A. Zolotov.

Chemistry. School encyclopedia. M .: - Bustard, "Great Russian Encyclopedia" 2003. - 872 p.

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